This invention relates to an acoustic ink printing method and system for improving uniformity by manipulating nonlinearity characteristics in the system. More particularly, the invention is directed to manipulation of the acoustic power output of the system relative to a power level at which nonlinearity of the system is onset. This is accomplished in the invention by a variety of techniques, including reducing the onset power level (of nonlinearity) and/or increasing the operating or output, power level such that the operating power level is greater than the onset power level.
While the invention is particularly directed to the art of acoustic ink printing, and will thus be described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications.
By way of background, acoustic ink printing involves the emitting of a droplet of ink from a pool of ink toward a print medium. Sound waves are generated and focussed toward the surface of the ink pool to emit the droplet therefrom. While acoustic ink printing elements may take various forms, such elements typically include a piezoelectric transducer, a lens, a cover plate having apertures formed therein to allow emission of the ink, and corresponding wiring. It is to be appreciated that approximately one thousand (1,000) or more of these elements may be disposed on a single printhead.
A difficulty with acoustic ink printing elements is that they are susceptible to a variety of factors that result in non-uniformity in the system. Such non-uniformity is undesirable because it causes non-uniformity in the emitted droplets, and thus reduces the precision, accuracy, and quality of the printing accomplished by the system.
Sources of non-uniformity in the system are many. For example, the cover plate may not be completely flat, causing the ink surface from which droplets are emitted to vary from ejector to ejector. Another source of non-uniformity is in the structure of the lens. This impacts on the efficiency of focussing the waves which cause the emission of the droplet from the surface of the ink.
Other sources of non-uniformity relate to the piezoelectric element. For example, nonuniform thickness of the piezoelectric element may influence the uniformity of operation across the printhead. In addition, certain inherent characteristics of the piezoelectric element, such as the electromechanical coupling constantxe2x80x94which determines the coupling between the electrical signal and the sound wavexe2x80x94may vary across the element and, thus, adversely impact uniformity of operation.
Still yet another source of non-uniformity in the system resides in the wiring patterns that are typically printed on the printhead. It should be appreciated that the resistance and reactance of these patterns cause non-uniformity to exist because the distances from the power source to different elements vary.
The present invention contemplates a new and improved acoustic ink printing method and system which resolve the above-referenced difficulties and others by manipulating the nonlinear characteristics of the system to compensate for the non-uniformities that may be present therein.
An acoustic ink method and system are provided for improving the uniformity in an acoustic ink printing system by manipulating nonlinear characteristics of the system. The invention includes operating the system at a power level that is above the power level at which the nonlinearity of the system is initiated in a variety of manners.
In one aspect of the invention, the density of the ink is reduced.
In another aspect of the invention, the nonlinearity constant of the ink is increased.
In another aspect of the invention, the F number of the lens is increased.
In another aspect of the invention, the frequency of the sound waves is increased.
In another aspect of the invention, the sound velocity of the sound waves through the ink is decreased.
In another aspect of the invention, the pulse width of the input RF pulse is reduced to increase peak operating power.
Further scope of the applicability of the present invention will become apparent from the detailed description provided below. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.